No. 435-] ANTITHETIC VERSUS HOMOLOGOUS. 1159 



Perhaps the strongest argument in favor of a common origin 

 for the sporophyte in all Archegoniates is the absolutely uniform 

 method of spore production. However ignorant we may be of 

 the transition from the motile zoospores resulting from the 

 germinating zygote of the green Algae to the immobile tetrad- 

 spores of the Archegoniates, there is no question as to the prac- 

 tical identity of the spores, both as to origin and structure 

 throughout not only the Archegoniates, but the seed-plants as 

 well. This extraordinary uniformity is perfectly comprehensible 

 if we accept the antithetic view, since the beginning of the sporo- 

 phyte must have been a simple mass of such spore-tetrads; and 

 in Ricciawe still have a sporophyte which has scarcely advanced 

 beyond this stage. In the more highly developed sporophytes 

 of the higher Archegoniates, the spores have retained their primi- 

 tive characters, but a continually increasing amount of the sporo- 

 phytic tissue has been devoted to purely vegetative purposes. 

 That this formation of spore-tetrads should invariably have taken 

 place in structures which are secondarily spore-producing, as is 

 demanded by the theory of a non-sexual origin for the sporo- 

 phyte in the Pteridophytes, requires something more than mere 

 hypothesis to give it much credence. This is all the more the 

 case if a poly phy let ic origin for the different phyla of Pteridoph- 

 ytes is assumed. 



Of all existing Bryophytes there is no question that Anthoce- 

 ros offers the nearest approach to the Pteridophytes, although 

 this by no means implies that the latter are directly derived from 

 the former. Were it not, however, for the form of the chroma- 

 tophores and spermatozoids in the Anthocerotacere I should not 

 hesitate to assume this to be the case. 



The sporophyte of Anthoceros is characterized by a long- 

 continued basal growth that adds to the tissues of the sporophyte, 

 which thus may reach a length of several centimeters. The 

 origin of the sporogenous tissue is like that of the Pteridophytes, 

 arising from sub-epidermal tissue, differing from all other Bryo- 

 phytes except Sphagnum in this respect. Moreover the sporo- 

 genous tissue is not continuous, but is more or less regularly 

 divided into sporogenous areas by intervening sterile tissue sug- 

 gesting an approach to a very simple form of sporangium. I he 



